The complexity of plant extract incurs the uncertainty of capping and reducing agents in the biosynthesis of silver nanoparticles (AgNPs) leading to a poor reproducibility, which dramatically limits the application of this method. To overcome this problem, the puerarin (Pue), which is an isoflavone derived from kudzu roots and has strong biological activities, is directly used as the reducing and capping agents to prepare bioactive AgNPs (Pue@AgNPs). The influence of biosynthesis parameters like pH (Pue solution), concentration of both Pue and AgNO₃ and incubation time were assessed to obtain Pue@AgNPs with superior bactericidal activity and photothermal effect. The as-prepared AgNPs are nearly spherical mainly existing in the monodispersed form with a small amount of aggregation, covering by anions (-44.0 mV) and revealing a high degree of stability (at least 15 days). It is conceived that the aggregation of Pue@AgNPs is responsible for absorbing near-infrared light (808 nm). The X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) studies show that Pue@AgNPs has a face-centered cubic (fcc) structure. The Pue@AgNPs show potent photothermal effect and antibacterial activity against Escherichia coli (E.coli), Staphylococcus aureus (S.aureus) and Methicillin-resistant Staphylococcus aureus (MRSA) under 808 nm laser radiation. The MIC values for E.coli, S.aureus and MRSA are 50.0 μg/mL. The internalization of Pue@AgNPs displays a variant trend suggesting the different mechanism of cell death. For E.coli, cell wall and intracellular damage may be responsible for cell death. However, for S.aureus and MRSA, the cell death may be rooted in oxidative stress or intracellular penetration. The Pue@AgNPs also exhibits superior antioxidation activity in trapping ABTS⁺ and DPPH radical, and could accelerate diabetic wound contraction and healing within 21 days. The histological analysis showed that Pue@AgNPs could reduce inflammation and accelerate the formation of blood and collagen deposition.

Key words: Puerarin, Silver nanoparticles, Photothermal effect, Antibacterial agent, Antioxidant, Wound dressing